Two things. First, your use of EXPR .. 1 contains an error. If $. == 1, the flip-flop will fail prematurely. Better would be to use a regexp that can never match. Second, an easy way to "reset" the flip-flop is by using eval:

sub blah {
    my $look_for = shift;
    my (undef, @a) = eval 'grep {$_ eq $look_for .. /(*FAIL)/} @_';
    @a;
}
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The eval forces a new flip-flop operator each time.